Point students to good resources: Purdue University provides excellent information on paraphrasing, quoting, and summarizing, plagiarism, and properly citing sources.
Include a plagiarism statement in your syllabi.
Tell your students that you check for plagiarism, then follow up. A good way to deter plagiarism is to develop a reputation for intolerance.
Create your assignments thoughtfully. Break the assignment into pieces, and provide due dates for each specific piece. Approve the topic, require drafts, require an annotated bibliography, current sources, and specify the style (ACS, AMA, APA, ASA, Chicago, CSE, MLA, Turabian, etc.) that students should use.
Have clear expectations. Require specific sources for your papers--one webpage, scholarly journal articles, scholarly books, a reference source, perhaps an interview. Make sure the sources students use have been published recently. Consider requiring the students to use a source provided by you.
The Learning Hub offers help to students in improving skills in writing, grammar and usage, math and statistics, science, reading, studying, test taking, and more. Click on "Writing" under "Academic Resources" to find tutorials and handouts on citation styles and other topics of interest to students writing papers.
The OWL at Purdue University houses writing resources and instructional material. Excellent guides for every major citation style, with sections on everything from paper formatting to in-text citations. Goes beyond citation guides to provide general writing resources as well.
This work first appeared in 1993. It was recently revised in January 2010 and reflects changes appearing in the third edition of the ALWD Citation Manual, published in 2006. It is also keyed to the most recent edition of The Bluebook, published in 2005.